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How to work with FPGA cores?

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Full Member level 4
Oct 8, 2001
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I am very unfamiliar with FPGA cores. So bear with my ignornance a bit.

I've seen many people refer to cores as if they were very common, but how does someone use a CORE made by someone else?

I have seen a 8051 VHDL core floating around but how does someone use it, what is it good for? Does Xilinx Foundation support the use of cores? if so how?

- Jayson

It depends on the type of core. A soft-core is delivered as a piece of HDL that you can synthesize along with your own HDL.
A hard-core is delivered as an (possibly even encrypted) netlist of gates (often EDIF-format) that you can still compile in your fitting tool. But if you look at the EDIF you won't find any meaningful netlist names so reverse engineering it would not be worthwile the effort.

Some tools encrypt the EDIF and have decryption keys built into the fitting tool so the user cannot see anything. The only thing you could look at is the post-place-and-route netlist. So there's not much to see, and making modifications is totally out of the question.

Hope this helps...

But what can you do with a core?
Why even use cores? are people too lazy to create their own stuff?

- Jayson


Why even use cores?

Think about DDC (digital down converter) core, I am workin on it for about 6 months and still nothing. The DDC is composed by multipliers, CIC FIR filters and SM to control all.

You can crate your own code (5 months) then you use simulator (1 month) and finaly you or your boss figure it out that this is not worth of your time.

that is why people use cores - time time time.


okay I have a VHDL 8051 core, how do I do something with it? How do I use inputs and outputs? How do I download my ASM compiled HEX code into it? What is the method from 1. obtaining core to 2. actually making use of it?

- Jayson

1.If you have VHDL core (8051) then use Xilinx FPGA to implement
you core. So you have real 8051 device.
implement way :
a. use Xilinx ISE5.1 to synthesis VHDL core , place and route, to get
VHDL netlist
b. post simulation VHDL netlist , if timing ok, then you get real 8051

2. design 8051 , EEPROM circuits, and you can put binary format
assembly in EEPROM , then you have small 8051 ststem

You may try use WebPack (you'll find it at It is freeware.

in fact, if you have no specaial idea of yourself, it is no use you do this. you have no any advantage.

everyone know ASIC8051 is very cheap,.

apacz said:
You may try use WebPack (you'll find it at It is freeware.
you are right,
but WebPack can't support some advanced FPGA, for eg, X2CV6000 ...

i think if you hope to use ip core,
the third-part tools are better.

Why IP cores?
I think, good IP cores can significantly reduce your time to market. This is true for both SOC
and FPGA design.

Hi ,

If it is a soft core,compile the core.

You instantiate the core in your code.

Then compile and synthesis it. Make the total design work according to your requirement by place and route.

It's very simple.

Take the core, instantiate it as many times as you want and download it into FPGA. This way u can create pretty complex systems on FPGA.

Would be nice to have A/D on FPGAs, would not be :).


Hi Lockerman

I agree with you. In addition to having ADC alone, having ADC & DAC would be very nice for DSP applications.


ADC or DAC on FPGA like "russian spacecraft jurney to Mars" you will never see that.

But there is a ADC core you can use.

go to


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